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Three signals the adjustment erased

GLP-1 users looked worse on three outcomes after shoulder surgery. Then the authors made the groups comparable and all three differences disappeared.

Glenn Torres5 min read
Before adjustment — odds ratio against no GLP-1urinary tract infection3.85stiffness2.20respiratory1.97After adjustment: none of them survived.

A near-fourfold rise in infections is the kind of number that travels. This one did not survive its own paper, and watching it die is more useful than any of the results.

The raw pass

Adults with type 2 diabetes undergoing rotator cuff repair between 2018 and 2024 were pulled from a research network and split by whether they filled a GLP-1 before surgery. [1] Compared directly, the users looked worse on three of the ninety-day outcomes.

Respiratory complications came in at an odds ratio of 1.97, 95% CI 1.32 to 2.86, p = 0.0006. Urinary tract infection at 3.85, 95% CI 1.31 to 9.12, p = 0.0055. Postoperative stiffness at 2.20, 95% CI 1.31 to 3.49, p = 0.0016. Three significant results pointing the same way — which is what an unmatched comparison usually looks like.

The adjusted pass

The authors then reweighted the sample so the two groups resembled each other on measured characteristics. Every difference vanished.

Nothing about the patients changed. Only the question did. The first pass asked whether GLP-1 users have more complications. The second asked whether taking one causes them. Those are two answers from one dataset.

Do not flip it into reassurance

Only 233 patients were exposed. That is a thin base for detecting a complication that happens to a small percentage of people.

So the honest reading is that this study found nothing, not that there is nothing to find. The authors say prospective work is needed, and they are right, because finding no difference is not the same as showing none exists.

What it is good for

A reader will meet the raw version of a number like this before the adjusted one. Social posts carry the 3.85. Papers carry the null.

The question to ask of any alarming figure about these drugs is whether the comparison group was built or just found. Most of what gets circulated about real-world GLP-1 use is the found kind, which is the whole difficulty with evidence collected outside a trial.

Frequently asked

Do GLP-1 drugs raise complication risk after shoulder surgery?
Not in this study once the comparison was adjusted. The raw figures showed more respiratory complications, urinary infections and stiffness, and none of it held up after propensity weighting.
Why did the numbers change so much?
Because people prescribed a GLP-1 for type 2 diabetes differ from those who are not. The unadjusted comparison was measuring who receives the prescription.
Does this prove the drugs are safe before surgery?
No. Only 233 of 5,876 patients were exposed, which is too few to rule out an uncommon complication. The authors call for prospective studies.
Is this about anesthesia risk?
No. This study counted complications over 90 days after surgery. Concerns about delayed stomach emptying during sedation are a separate question with its own evidence.

Sources

  1. [1] Choudhury A, et al. (2026). The impact of glucagon-like peptide-1 (GLP-1) receptor agonists on postoperative outcomes following rotator cuff repair Shoulder & Elbow. PMID 42712738

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